U.S. Pat. No. 4,361,559 to Varma discloses antiinflammatory 17,17-bis(substituted thio)androstenes of the formula ##STR1## wherein
R.sub.1 and R.sub.2 are the same or different and each is alkyl, cycloalkyl or aryl;
R.sub.3 is hydrogen, hydroxy, alkoxy, aryloxy, alkylthio, arylthio, ##STR2## or halogen;
R.sub.4 is hydrogen, methyl, hydroxy, ##STR3## or halogen;
R.sub.5 is hydrogen or halogen; and
R.sub.6 is carbonyl or .beta.-hydroxymethylene. A broken line in the 1,2-, 6,7- and 15,16-position of a structural formula indicates the optional presence of ethylenic unsaturation.
Included among the compounds covered in the Varma patent is tipredane which has been found to be a highly effective topical antiinflammatory agent.
Tipredane is practically insoluble in water (less than 0.0002 mg/ml at 25.degree. C.); 1:1 hydroalcoholic mixtures of tipredane are unstable under acidic conditions. Further, tipredane itself is susceptible to oxidation. It has been found that propylene glycol is an excellent solubilizer for tipredane and a good preservative. However, where it has been attempted to formulate a tipredane ointment containing propylene glycol and an ointment base such as Plastibase (mineral oil gelled with polyethylene) or petrolatum, it has been found that when propylene glycol is dispersed in Plastibase or petrolatum, the propylene glycol coalesces and separates out of the Plastibase or petrolatum.
Until now, attempts to prepare a stable ointment formulation containing tipredane which overcomes the above formulation problems have not been successful.